CIVIL ENGINEERING FORMULAS

TIMBER ENGINEERING FORMULAS 169

The beam stability factor CLmay be calculated from

(6.34)

where design value for bending multiplied by all applicable adjustment
factors, except Cfu,CV, and CL

FbE

0.438 for visually graded lumber and machine-evaluated lumber

0.609 for products with a coefficient of variation of 0.11 or less

design modulus of elasticity multiplied by applicable adjustment

factors

FASTENERS FOR WOOD

Nails and Spikes

The allowable withdrawal load per inch (25.4 mm) of penetration of a common
nail or spike driven into side grain (perpendicular to fibers) of seasoned wood,
or unseasoned wood that remains wet, is

(6.35)

wherepallowable load per inch (mm) of penetration into member receiving
point, lb (N)
Ddiameter of nail or spike, in (mm)
Gspecific gravity of wood, oven dry

The total allowable lateral load for a nail or spike driven into side grain of
seasoned wood is

(6.36)

wherepallowable load per nail or spike, lb (N)
Ddiameter of nail or spike, in (mm)
Ccoefficient dependent on group number of wood (see Table 6.1)

Values of Cfor the four groups into which stress-grade lumber is classified are

Group I: C2,040

Group II: C1,650

Group III:C1,350

Group IV:C1,080

pCD3/2

p1,380G5/2D

E

KbE

KbEE/R^2 B

F*b

CL

1 (FbE/Fb*)

1.9



B

1 (FbE/Fb*)

1.9 

2



FbE/Fb*

0.95